For example, one of such fuel cell stacks in the art is described in Patent Document 1. The fuel cell stack described in Patent Document 1 includes electrolyte-electrode assemblies and metal separators that are alternately stacked in the horizontal direction, in which fluid communication holes (manifolds) for coolant or reaction gas penetrate in the stacking direction. Further, the fuel cell stack is configured such that insulative members are provided to the metal separators to cover the surfaces of the metal separators and the inner walls of the fluid communication holes so that the sealing property against the coolant or the reaction gas is secured by means of the insulative members.